The Foreign Secretary said he found the result of Ms Gibbons’ trial “deeply disappointing” and “expressed in the strongest terms” his concern over the jail sentence handed to the Liverpool teacher.

Following the verdict, Mr Miliband summoned the Sudanese ambassador, Omer Siddig, to explain the decision.

Mr Miliband held a 15-minute phone conversation with the Sudanese acting foreign minister during the meeting with the Sudanese ambassador.

In a statement last night the Foreign Office said: “During the meeting, which lasted 45 minutes, the Foreign Secretary expressed in the strongest terms our concern at the continued detention of Gillian Gibbons.

“The Foreign Secretary also spoke to the Sudanese acting foreign minister for 15 minutes on the telephone during the meeting.

“There will be further contacts overnight and tomorrow in the search for a swift resolution of this issue.”

Her jailing came despite the Foreign Secretary David Miliband earlier insisting British concerns over her ordeal were being addressed at the “highest level” of Sudan’s government.

Britain reacted furiously to the sentence and Mr Miliband had repeated his belief that the teacher had made an “innocent mistake” in allowing her six and seven-year-old pupils to name a teddy bear Mohammed.

Ms Gibbons, from Liverpool, could have been jailed for up to six months in jail or faced 40 lashes in a public flogging.

It also emerged yesterday that the initial allegations against the mother-of-two were made by the secretary of the Sudanese school, and not a parent of the pupil of the school as was claimed.

Prior to the sentencing, Mr Miliband had tried to set out the UK’s “real respect” for Sudan’s Islamic religion after a first meeting with the ambassador.

“Britain has also enjoyed close relations with Sudan for many years based on our mutual respect for each other’s religious and cultural values,” he said.

“The Sudanese ambassador undertook to ensure our concerns were relayed to Khartoum at the highest level.”

The Deputy Prime Minister, Harriet Harman, had also pledged full support for the British teacher during a debate in the House of Commons.

She said: "The Government, and I’m sure everybody, will want to be sure that she can be back home where she belongs, free, as soon as possible.”